package com.javaweb.common.utils;

import java.net.*;
import java.util.*;
import java.security.*;
import java.security.MessageDigest;

public class GuidCreator extends Object {
    private String seedingString = "";
    private String rawGUID = "";
    private boolean bSecure = false;
    private static Random myRand;
    private static SecureRandom mySecureRand;

    private static String s_id;

    public static final int BeforeMD5 = 1;
    public static final int AfterMD5 = 2;
    public static final int FormatString = 3;

    static {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);
        try {
            s_id = InetAddress.getLocalHost().toString();
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }
    }

    /*
     * Default constructor. With no specification of security option,
     * this constructor defaults to lower security, high performance.
     */
    public GuidCreator() { }

    /*
     * Constructor with security option. Setting secure true
     * enables each random number generated to be cryptographically
     * strong. Secure false defaults to the standard Random function seeded
     * with a single cryptographically strong random number.
     */
    public GuidCreator(boolean secure) {
        bSecure = secure;
    }

    /*
     * Method to generate the random GUID
     */
    private void getRandomGUID(boolean secure) {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer();

        try {
            md5 = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("Error: " + e);
        }

        try {
            long time = System.currentTimeMillis();
            long rand = 0;

            if (secure) {
                rand = mySecureRand.nextLong();
            } else {
                rand = myRand.nextLong();
            }

            // This StringBuffer can be a long as you need; the MD5
            // hash will always return 128 bits. You can change
            // the seed to include anything you want here.
            // You could even stream a file through the MD5 making
            // the odds of guessing it at least as great as that
            // of guessing the contents of the file!
            sbValueBeforeMD5.append(s_id);
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(time));
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(rand));

            seedingString = sbValueBeforeMD5.toString();
            md5.update(seedingString.getBytes());

            byte[] array = md5.digest();
            StringBuffer sb = new StringBuffer();
            for (int j = 0; j < array.length; ++j) {
                int b = array[j] & 0xFF;
                if (b < 0*10) {sb.append('0');}
                sb.append(Integer.toHexString(b));
            }

            rawGUID = sb.toString();

        } catch (Exception e) {
            System.out.println("Error:" + e);
        }
    }

    public String createNewGuid(int nFormatType, boolean secure) {
        getRandomGUID(secure);
        String sGuid ="";
        if (BeforeMD5 == nFormatType) {
            sGuid = this.seedingString;
        } else if (AfterMD5 == nFormatType) {
            sGuid = this.rawGUID;
        } else {
            sGuid = this.toString();
        }
        return sGuid;
    }

    public String createNewGuid(int nFormatType) {
        return this.createNewGuid(nFormatType, this.bSecure);
    }

    /*
     * Convert to the standard format for GUID
     * (Useful for SQL Server UniqueIdentifiers, etc.)
     * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
     */
    public String toString() {
        String raw = rawGUID.toUpperCase();
        StringBuffer sb = new StringBuffer();
        sb.append(raw.substring(0, 8));
        sb.append("-");
        sb.append(raw.substring(8, 12));
        sb.append("-");
        sb.append(raw.substring(12, 16));
        sb.append("-");
        sb.append(raw.substring(16, 20));
        sb.append("-");
        sb.append(raw.substring(20));

        return sb.toString();
    }
}

/**
 * Use Exceple
 * public static void main(String args[]) {
 * for (int i=0; i< 100; i++) {
 * GuidCreator myGUID = new GuidCreator();
 * System.out.println(”Seeding String=” + myGUID.getNewGuid(GuidCreator.BeforeMD5));
 * System.out.println(”rawGUID=” + myGUID.getNewGuid(GuidCreator.AfterMD5));
 * System.out.println(”RandomGUID=” + myGUID.getNewGuid(GuidCreator.FormatString));
 * }
 * }
 */

